Physical Damage

Physical is one of the types of damage in Diablo III. It is non-elemental and also referred to as "black" damage as opposed to the colorful effects tied to all elemental damage types.

Like other forms of damage, Physical can be mitigated by physical resistance. It it also affected by armor.

Black Weapons

Diablo 3 classic has a bug with physical damage that is most commonly seen on the so-called "black weapons." This causes some +%damage modifiers to deal much higher damage when modifying "black" weapons than when acting upon all elemental types of damage. See the black weapons article for full details.

This bug was fixed in regards to Rubies in weapons in Patch 1.0.7 and will be fixed entirely on weapons dropping in Loot 2.0 and in Reaper of Souls.